Docs: Update couchdb/README.md - change cookeAuthSecret to erlangCookie and make code blocks easier to copy via copy button on github

[jessebot]

What this PR does / why we need it:

This updates cookeAuthSecret to erlangCookie in the README for the helm chart directory, as that is what couchdb looks for in the secret can pre-generate.

I've also updated the code blocks to not have $ in front of each command, so that users can more easily copy and paste the commands to test them. This is particularly helpful for users with disabilities as they don't need to mind the space and dollar sign when trying out the commands in the docs.

Which issue this PR fixes

• doesn't completely cover, but helps address Update Installation Guide #101

Special notes for your reviewer:

Thanks for maintaining this helm chart!

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.

• Variables are documented in the README.md

[willholley]

Thanks for the PR! As per my review comment, I think the change to the secrets documentation is an "and" rather than an "or", since both secret values are required.